A recent published report linked the administration of sublingual nitroglycerin with subsequent arterial hypoxemia in patients undergoing coronary artery bypass grafting. We have designed a protocol to investigate the following: 1) to determine whether sublingually administered nitroglycerin causes a decrease in arterial oxygen tension; 2) to determine the degree of arterial hypoxemia sublingual nitroglycerin may cause in patients with coronary artery disease; 3) to investigate the mechanism of action, if sublingual nitroglycerin does cause a reduction in arterial oxygen tension.